Probenecid and Colchicine

INDICATIONS AND USAGE For the treatment of chronic gouty arthritis when complicated by frequent, recurrent acute attacks of gout.

DOSAGE AND ADMINISTRATION Therapy with probenecid and colchicine should not be started until an acute gouty attack has subsided. However, if an acute attack is precipitated during therapy, probenecid and colchicine may be continued without changing the dosage, and additional colchicine or other appropriate therapy should be given to control the acute attack. The recommended adult dosage is 1 tablet of probenecid and colchicine daily for one week, followed by 1 tablet twice a day thereafter. Some degree of renal impairment may be present in patients with gout. A daily dosage of 2 tablets may be adequate. However, if necessary, the daily dosage may be increased by 1 tablet every four weeks within tolerance (and usually not above 4 tablets per day) if symptoms of gouty arthritis are not controlled or the 24 hour uric acid excretion is not above 700 mg. As noted, probenecid may not be effective in chronic renal insufficiency particularly when the glomerular filtration rate is 30 mL/minute or less. Gastric intolerance may be indicative of overdosage, and may be corrected by decreasing the dosage. As uric acid tends to crystallize out of an acid urine, a liberal fluid intake is recommended, as well as sufficient sodium bicarbonate (3 to 7.5 g daily) or potassium citrate (7.5 g daily) to maintain an alkaline urine (see PRECAUTIONS ). Alkalization of the urine is recommended until the serum urate level returns to normal limits and tophaceous deposits disappear, i.e., during the period when urinary excretion of uric acid is at a high level. Thereafter, alkalization of the urine and the usual restriction of purine-producing foods may be somewhat relaxed. Probenecid and colchicine (or probenecid) should be continued at the dosage that will maintain normal serum urate levels. When acute attacks have been absent for six months or more and serum urate levels remain within normal limits, the daily dosage of probenecid and colchicine may be decreased by 1 tablet every six months. The maintenance dosage should not be reduced to the point where serum urate levels tend to rise.

CONTRAINDICATIONS Hypersensitivity to this product or to probenecid or colchicine. Probenecid and colchicine tablets are contraindicated in children under 2 years of age. Not recommended in persons with known blood dyscrasias or uric acid kidney stones. Therapy with probenecid and colchicine should not be started until an acute gouty attack has subsided. Pregnancy: Probenecid crosses the placental barrier and appears in cord blood. Colchicine can arrest cell division in animals and plants. In certain species of animals under certain conditions, colchicine has produced teratogenic effects. The possibility of such effects in humans also has been reported. Because of the colchicine component, probenecid and colchicine is contraindicated in pregnant patients. The use of any drug in women of childbearing potential requires that the anticipated benefit be weighed against the possible hazards.

ADVERSE REACTIONS To report SUSPECTED ADVERSE REACTIONS, contact Ingenus Pharmaceuticals NJ, LLC at 1-877-748-1970 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. The following adverse reactions have been observed and within each category are listed in order of decreasing severity. Probenecid Central Nervous System: headache, dizziness. Metabolic: precipitation of acute gouty arthritis. Gastrointestinal : hepatic necrosis, vomiting, nausea, anorexia, sore gums. Genitourinary: nephrotic syndrome, uric acid stones with or without hematuria, renal colic, costovertebral pain, urinary frequency. Hypersensitivity: anaphylaxis, fever, urticaria, pruritus. Hematologic: aplastic anemia, leukopenia, hemolytic anemia which in some patients could be related to genetic deficiency of glucose-6- phosphate dehydrogenase in red blood cells, anemia. Integumentary: dermatitis, alopecia, flushing. Colchicine Side effects due to colchicine appear to be a function of dosage. The possibility of increased colchicine toxicity in the presence of hepatic dysfunction should be considered. The appearance of any of the following symptoms may require reduction of dosage or discontinuance of the drug. Central Nervous System: peripheral neuritis. Musculoskeletal: muscular weakness. Gastrointestinal: nausea, vomiting, abdominal pain, or diarrhea may be particularly troublesome in the presence of peptic ulcer or spastic colon. Hypersensitivity: urticaria. Hematologic: aplastic anemia, agranulocytosis. Integumentary: dermatitis, purpura, alopecia. At toxic doses, colchicine may cause severe diarrhea, generalized vascular damage, and renal damage with hematuria and oliguria.

Drug Interactions When probenecid is used to elevate plasma concentrations of penicillin, or other beta-lactams, or when such drugs are given to patients taking probenecid therapeutically, high plasma concentrations of the other drug may increase the incidence of adverse reactions associated with that drug. In the case of penicillin, or other beta-lactams, psychic disturbances have been reported. The use of salicylates antagonizes the uricosuric action of probenecid (see WARNINGS ). The uricosuric action of probenecid is also antagonized by pyrazinamide. Probenecid produces an insignificant increase in free sulfonamide plasma concentrations but a significant increase in total sulfonamide plasma levels. Since probenecid decreases the renal excretion of conjugated sulfonamides, plasma concentrations of the latter should be determined from time to time when a sulfonamide and probenecid and colchicine are coadministered for prolonged periods. Probenecid may prolong or enhance the action of oral sulfonylureas and thereby increase the risk of hypoglycemia. It has been reported that patients receiving probenecid require significantly less thiopental for induction of anesthesia. In addition, ketamine and thiopental anesthesia were significantly prolonged in rats receiving probenecid. The concomitant administration of probenecid increases the mean plasma elimination half-life of a number of drugs which can lead to increased plasma concentrations. These include agents such as indomethacin, acetaminophen, naproxen, ketoprofen, meclofenamate, lorazepam, and rifampin. Although the clinical significance of this observation has not been established, a lower dosage of the drug may be required to produce a therapeutic effect, and increases in dosage of the drug in question should be made cautiously and in small increments when probenecid is being co-administrated. Although specific instances of toxicity due to this potential interaction have not been observed to date, physicians should be alert to this possibility. Probenecid given concomitantly with sulindac had only a slight effect on plasma sulfide levels, while plasma levels of sulindac and sulfone were increased. Sulindac was shown to produce a modest reduction in the uricosuric action of probenecid, which probably is not significant under most circumstances. In animals and in humans, probenecid has been reported to increase plasma concentrations of methotrexate (see WARNINGS ). Falsely high readings for theophylline have been reported in an in vitro study, using the Schack and Waxler technique, when therapeutic concentrations of theophylline and probenecid were added to human plasma.

DESCRIPTION Probenecid and colchicine contains probenecid, which is a uricosuric agent, and colchicine, which has antigout activity, the mechanism of which is unknown. Probenecid is the generic name for p-(Dipropylsulfamoyl)benzoic acid. The structural formula is represented below: C 13 H 19 NO 4 S M.W.285.36 Probenecid is a white or practically white, fine, crystalline powder. It is soluble in dilute alkali, in alcohol, in chloroform, and in acetone; it is practically insoluble in water and in dilute acids. Colchicine is an alkaloid obtained from various species of Colchicum. The chemical name for Colchicine is (S)-N-(5,6,7,9- tetrahydro-1,2,3,10-tetramethoxy-9-oxobenzo[α]heptalen-7-yl) acetamide. The structural formula is represented below: C 22 H 25 NO 6 M.W.399.44 Colchicine consists of yellowish white to pale yellow to pale greenish-yellow powder which darken on exposure to light. Colchicine is freely soluble in chloroform. Each tablet for oral administration contains 500 mg of probenecid and 0.5 mg of colchicine. Each tablet also contains the following inactive ingredients: colloidal silicon dioxide, corn starch, magnesium stearate, microcrystalline cellulose, povidone, sodium lauryl sulfate and sodium starch glycolate. FDA approved dissolution test specifications differ from the USP. probenecid-struc.jpg colchicine-struc.jpg

HOW SUPPLIED Probenecid and Colchicine Tablets, USP 500 mg/0.5 mg are bisected, white to off-white capsule shaped, tablets debossed with “C81” on one side and break line on another side. They are supplied in bottles of 100 count: NDC 16571-832-01 Dispense in a well closed, light-resistant container with child-resistant closure. Store at 20o to 25oC (68o to 77oF); excursions permitted to 15° to 30°C (59° to 86°F) [See USP Controlled Room Temperature]. Protect from light. Manufactured for: Rising Pharma Holdings, Inc. East Brunswick, NJ 08816 Made in India. Neutral Code: 4323066/TS/DRUGS/2025 Revised: 01/2026 PIR83201-05